"The most difficult problems are found in the simplest things."

"How often have I said to you that when you have eliminated the impossible, whatever remains, however improbable, must be the truth?"

"I have no doubt that there are other planets inhabited by intelligent beings."

"Detection is, or ought to be, an exact science and should be treated in the same cold and unemotional manner."

"It is only when you touch the higher that you realize how low we may be among the possibilities of creation."